Uninterrupted power supply (UPS) system interfacing with communications network

ABSTRACT

There is a provided a system of one or more uninterrupted power supply (UPS) units, each UPS unit having distributed processing system and a network interface for interfacing with a local area network, the network providing a communication between the one or more UPS devices and also to loads powered by such UPS devices. In one embodiment having a plurality of UPSs, one of the UPSs is a main upstream UPS which is in communication with each down stream UPS to which it supplies supplemental power and which in turn supply power to respective loads. In another embodiment the UPS supplies power to a plurality of prioritized loads, and is in communication with each such load over a network and also controls power distribution to each such load through a power distribution module (PDM).

This is a division of application Ser. No. 07/980,650, filed Nov. 24,1992, U.S. Pat. No. 5,319,571.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a system for communicating to or from one ormore UPS devices through a network and, more particularly to adistributed processing system wherein each UPS is connected directlythrough a network interface unit to a local area network (LAN).

2. Description of the Prior Art

The uninterrupted power supply (UPS) has become indispensable for manymodern day power loads. Particularly with respect to computers and otherforms of data processing devices, it is of utmost importance that powerbe uninterrupted so that automated systems do not go down, data is notlost, etc. UPS devices are thus in widespread use for a variety ofloads, but are particularly critical to the computer or processorenvironment.

Of particular importance to this invention is the situation where poweron the utility line is lost for sufficient duration that the load mustshut down. As is known, in the event of power loss the UPS providesuninterrupted power that looks like utility power, so that the load isunaffected. However, for a given load, any UPS or package of UPSs willbe able to maintain power to the load for only a limited amount of time,dependent upon the energy stored in its batteries. In the computersituation, when and if power has been lost for a period of timeapproaching the total battery time which the UPS can supply, steps mustbe taken to shut down the load in an optimized manner. For instance, anidle printer or an idle tape drive or terminal could be powered down toconserve the battery for the main frame. Intelligence is thus needed tocontinuously monitor the time of power loss, and perform sequentialpreprogrammed load shedding of the computer hardware on the network, inorder to maintain necessary operations for as long as possible during apower outage, and to download data onto a storage medium which is notaffected by power loss.

The prior art has recognized the need to communicate between a networkto which a number of computer loads are attached, ant each UPS that isbeing used in connection with such computers. However, the direction ofthe solution has been to provide software at the computer, orworkstation, which simply enables it to receive alarm and statusnotification from the UPS. The prior art provides no system orarrangement for sending control signals from an UPS to any other UPS.Further, the prior art does not provide the UPS with the capability ofturning itself off or on, or of providing programmed sequential loadshedding.

Referring to FIG. 1, there is shown a simplified diagram of the priorart approach to communications involving a network, a plurality of nodes(some of which may be workstations), and a UPS associated with eachnode. In this arrangement, each UPS is shown powering the load at anetwork node, although more complicated arrangements are possible. Thenetwork nodes are tied together by an appropriate cable, using"EtherNet." See IEEE 802.3 10 Base 5 (thick wire) and 10 Base 2 (thinwire) standards. The EtherNet transports packets of data between nodes,and each workstation uses "Proxy Agent" software to communicate with itsrespective UPS. The UPS can provide its workstation with alarm andstatus notification, over the RS-232 link between them. However, not allnodes are workstations, and there is no capability for sending anycontrol or sequence signals from a UPS to any other UPS or directly toany other computer on the network. Further, if any given UPS providesthe power to one or more downstream UPSs, the upstream UPS cannot sendshutdown instructions to such a downstream UPS. The system is thuslimited, and each UPS is without its own capacity to receive andgenerate controls for itself or other UPSs.

SUMMARY OF THE INVENTION

It is a primary object of this invention to provide an interconnectedsystem of UPS units, or a single UPS tied to plural loads, each UPS unithaving a network interface board or card for interfacing with acommunications network whereby each such UPS is an effective node thatcommunicates directly with the local network. In one preferredembodiment, a large upstream UPS powers each of the other UPS devices,has means to instruct each downstream UPS when AC power has been lost,and to control the timing of shutdown of each downstream device. EachUPS network interface means has a microprocessor and associated memory,providing for distributed control of shutdown, thereby maintaining powerto priority loads for the maximum available time, and enablingdownloading of critical data into safe storage. In another embodiment, asingle UPS communicates through the network to plural loads in order toprovide programmed load shedding in event of utility power loss.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram illustrating a prior artarrangement.

FIG. 2 is a block diagram of one embodiment of the system of thisinvention, whereby each UPS has its own means of interfacing with anetwork, thereby providing for distributed control of power delivery torespective loads.

FIG. 3 is a block diagram of a network interface board, or card, asemployed in each UPS in accordance with this invention.

FIG. 4A is a simplified flow diagram illustrating the basic controldecisions carried out in the upstream main UPS of the system of FIG. 2.

FIG. 4B is a flow diagram illustrating the primary decisions made ineach downstream UPS of the system of FIG. 2.

FIG. 5 is a block diagram of another embodiment of the system of thisinvention, whereby a UPS communicates with plural loads over an LAN modeto achieve prioritized load shedding in the event of power loss.

FIG. 6 is a simplified flow diagram of the routine in the UPS of FIG. 5,for controlling prioritized load shedding.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 2, there is shown a simplified block diagram ofone of the preferred embodiments of this invention. In this system, aplurality of loads receive power from respective downstream UPS units,which downstream UPS units in turn receive supplemental power from anupstream, larger power UPS. As seen in FIG. 2, the utility line 31provides power to a first, or upstream UPS 32. UPS 32 providesuninterrupted power on line 34, which line provides supplemental powerto downstream UPS devices 36, 38, etc. Each downstream UPS providespower to a respective load, illustrated at 37 and 39. In thisarrangement, each downstream UPS has its own battery supply, andnormally receives power from upstream UPS 32 instead of directly fromthe utility. In the case of loss of power on the utility line, eachdownstream UPS can continue to provide power to its load derived bothfrom its own battery, and also battery-generated power coming fromupstream UPS 32. In addition, UPS 32 may independently supply one ormore loads, as illustrated at 42, 43.

Still referring to FIG. 2, a network 45, suitably utility "EtherNet",interconnects the UPS devices (and may also connect to the loads). EachUPS device has a network interface card (NIC) or network interface board50, which interconnects between the main conventional UPS controls andnetwork 45. By having an NIC 50 in each UPS, the system is provided withdistributed processing capability, whereby each UPS can communicate withthe others, and thus can make logic decisions based upon receivedinformation as well as on the basis of its own status readings. By thisarrangement, the main or upstream UPS 32 can tell each downstream UPSwhen ac power has been lost and its battery status, whereby eachdownstream UPS can intelligently control timing of its own shutdown.Contrasted with the prior art arrangement of FIG. 1, in this system eachUPS is a node that communicates directly with the network.

Referring now to FIG. 3, there is illustrated a block diagram of the NIC50. The network cable 45 is connected to the network interface 57, astandard commercially available IC, for providing I/O between the UPSand the network. The network interface is coupled to network controller56, also a commercially available IC. Controller 56 handles low leveldata link control, e.g., error correction, decoding of data coming offthe network, encoding data for placing on the network, etc. Interfaceblock 51, also a standard available circuit, interconnects between themain UPS controls and a microprocessor 52. Microprocessor 52 providesthe processing capability required for the decision routines asdiscussed below. Microprocessor 52 is interconnected with program memoryillustrated at 54, and read/write memory 55 which is showninterconnected between the microprocessor 52 and network controller 56.

Referring now to FIGS. 4A and 4B, there are shown UPS flow diagrams foran embodiment of the invention directed to controlling UPS shutdown forthe system of FIG. 2. FIG. 4A is flow diagram for the upstream UPS,while FIG. 4B illustrates a downstream UPS shutdown control flowdiagram. The software for carrying out these routines is suitably storedin program memory 54. It is to be understood that these flow diagramsare illustrative only of a control routine for the system embodimenthaving a large upstream UPS and plural smaller downstream UPSs connectedthereto.

Referring to FIG. 4A, at 62 the processor determines whether shutdown isimminent. Shutdown would be imminent, for example, in the case ofutility power loss and low battery simultaneously occurring.Alternately, UPS 32 may have received a communication from network 45directing it to shutdown. If shut, down is not imminent, the programbranches to block 64, and determines whether it has received a requestfrom one of the other UPS units to send a packet of data. Such a packetof data is referred to as a status data packet, and contains UPS statestatus as well as battery time remaining. If there has been no suchrequest, the UPS recycles to block 62. If there has been such a request,the program branches directly to block 66, and sends a status datapacket onto the network.

Referring now to FIG. 4B, at block 71 the downstream UPS can request apacket from the upstream UPS. Following this, at block 72 it isdetermined whether a packet has been received. If no, the routine waitsat 73, and then again determines whether it has been received. Once thepacket has been received, the program branches to block 75, where it isdetermined whether the upstream UPS is on line, i.e., is it puttingpower out. If no, then the downstream UPS knows that it is on its own,and it branches to block 76 where its effective battery time is setequal to its own local battery time. Following this, the programbranches to block 80. If the answer at block 75 is yes, i.e., theupstream UPS is on line, the program first branches to block 77, andsets effective battery time to be equal to the upstream time plus localtime, and then to block 78. At block 78, it is determined whether theupstream UPS is on battery, an indication that power has been lost. Ifno, the program branches to block 79 and determines whether the UPS hasreceived an unrequested packet. If yes, the program branches back toblock 75; if no, it goes back to block 71. If the answer at 78 is yes,the routine proceeds to block 80, to determine whether its localpriority has expired. The local priority is programmed into each UPS,and is the determinant of how long it can continue to receivesupplemental power from the upstream UPS. If the local priority has notexpired, the program branches to block 79. If it has expired, theprogram proceeds to block 81, where it is determined whether it is timeto shut down the downstream UPS. If no, the program branches to block84, where a warning is given to the user of the number of minutesremaining, i.e., how much longer such UPS will continue to provide powerto its load. If at 81 it is determined that it is time to shut down, thecontrol branches to block 85 where shutdown is undertaken in accordancewith a predetermined program. The shutdown routine for each UPS may besimple or complex, depending upon the loads that it is supplying. Thus,for example, each UPS in turn may prioritize its respective loads andshut them down in a predetermined manner.

Referring now to FIG. 5, there is shown another embodiment whereby a UPSis equipped with an NIC for controlling downloading of a plurality ofloads to which it is supplying power. In this arrangement, a single UPS95 is shown receiving power from the power line 31. The UPS has abattery 91 and an NIC 50. Associated with it is a power distributionmodule, PDM, 90. The PDM contains logic controlled breakers which allowfor selective load shedding of the various loads supplied by UPS 95. Inthe arrangement illustrated, UPS 95 supplies power to loads 100-103,having priorities 0, 1, 2 and 3 respectively. The assigned priority foreach load determine how long it will receive power from the UPS in theevent of shutdown, as is illustrated below in connection with thediscussion of the flow diagram for controlling shutdown. In thisarrangement, the NIC 50 communicates with the network, e.g., EtherNet45, which in turn communicates with each of loads 100-103. In thissystem, each load, or node on the network, is an intelligent device,e.g., a computer. This embodiment of the invention provides forcommunication between the UPS and each computer, and incorporates theability to perform sequential load shedding of hardware on the networkin order to keep the high priority loads operational for as long aspossible during a power outage. This embodiment thus provides fortotally automatic shutdown, as well as restart capability, by employingsequential power switching through the PDM and the network commands. Itis also noted that with this arrangement an instruction to shut down anyone of the computers for any given reason, can be communicated from anexternal node to the EtherNet, and acted on by the UPS.

Referring now to FIG. 6, there is shown a flow diagram for carrying outan automatic shutdown sequence. In this flow diagram, it is assumed thatthere are four loads, having power protection priorities in the range of0 to 3, with 0 being the lowest priority and 3 being the highestpriority. It is, of course, understood that the invention is not limitedto the number of loads or the complexity of the shutdown sequence, andthis flow diagram is illustrative.

During quiescent operation, the UPS waits and monitors the power line todetermine whether there is loss of utility power. If such power loss isdetermined at block 110, the UPS routine proceeds to block 112 and sendsa message to all loads, via network 45, indicating that the UPS is nowrunning on battery. Assuming that the UPS battery time is specified atsix minutes, the program then waits for one minute to pass, such thatfive minutes of battery time is remaining (114). When this isdetermined, at 116 the UPS sends a message via the network to all lowestpriority (priority level 0) devices, warning that they will shut down intwo minutes. The computer that receives this information can respondintelligently, by in turn selectively shutting down portions which arenot in use or which are lower priority. Following this, at block 118,the UPS waits until four minutes of battery time remain, at which timeit proceeds to block 120 and sends a warning message via the network toall priority 1 devices that they will be shut down in two minutes. At122, the UPS waits until only three minutes of battery time remain, atwhich time the UPS sends a warning message via the network to allpriority level 2 devices that they will shut down in two minutes, asseen at 126. At the same time, the UPS opens the breaker or breakersthat feed the priority level 0 devices. This may, and probably should,cause the predicted battery time remaining to increase, due to thedecreased load being handled by the UPS. Subsequently, at block 128, theUPS recalculates the battery time, and at 130 broadcasts revisedwarnings to priority 1 devices, e.g., advises if the new predictedbattery time is greater than five minutes.

Following this, the UPS waits until two minutes of battery time remain,as shown at block 132. At this time, a warning message is sent via thenetwork to all priority level 3 devices, advising that they will be shutdown in two minutes, as seen at block 134. At the same time, the UPScontrols the PDM to open the breaker or breakers that feed the prioritylevel 1 devices, as seen at 136. Following this, at 138, the UPSrecalculates remaining battery time, and sends any revised time to thelevel 2 devices. At 140, the UPS waits until only one minute isremaining, and then at 142 causes the PDM to open the breaker orbreakers that feed the priority level 2 devices. Again, this may causethe predicted remaining battery time to increase, so this value isrecalculated at 144. A message is sent to all level three devicescontaining the recalculated time, as seen at 146. The UPS then waits at148 until a determination that 0 battery time is left, at which time itremoves power from all remaining loads, including the priority 3 leveldevices, as shown at 150.

We claim:
 1. A system comprising an uninterrupted power supply (UPS), aplurality of loads having predetermined priorities for maintenance ofpower thereto, a network for transmitting data to and from each of saidloads and said UPS, and bar connection means for connecting powerseparately from said UPS to each of said loads, said UPS having networkinterface means for interfacing with said network, said networkinterface means further comprising processor means for processing dataand control signal generating means for generating control signals forcontrolling connection of power to each of said loads, said processormeans comprising first means for generating messages to each of saidloads wherein said messages concern time remaining for receipt of powerby such load, and second means for generating shutdown signals andconnecting said shutdown signals to said control signal generating meansfor controlling prioritized shutdown of said loads.
 2. The system asdescribed in claim 1, wherein said control signal generating meanscomprises a power distribution module (PDM) for controlling distributionof power to said loads.
 3. The system as described in claim 1, whereinsaid processor means comprises storage means for storing datarepresentative of the predetermined priorities of said plurality ofloads.